Spring hanger

ABSTRACT

Apparatus for suspending vertically disposed furnace tubes. A compression spring provided with spacers is arranged within a tubular casing having interior walls coated with a low-friction material to facilitate aligned compression of the spring. Calibrated load indicating means are also arranged to accurately display the load imposed thereon.

O Umted States Patent 1151 3,637,174 Kuo 1451 Jan. 25, 1972 54] SPRING HANGER 2,421,822 6/l947 Wood ..248/54 2,480,487 7/1949 Loepsinger. [721 lnvemo" 511mg Kuo, sclwatey Mass- 2,873,078 2/1959 Suozzo .243/54 73 Assisnee: stone & Webster Engineering p 2,937,765 5/1960 Shank ..21 1/143 Mass FOREIGN PATENTS OR APPLICATIONS [22] 1969 697,987 10 1953 Great Britain ..248/54 121 1 Appl. No.: 854,709

Primary ExaminerChancellor E. Harris 52 us. c1 ..248/54, 267/168 F'nnegan Durham pm [51] Int. Cl. 1 ..Fl6l 3/20 57 [58] Field of Search ..248/54, 54 CS; 267/166, 168 I 1 Apparatus for suspending vertically disposed furnace tubes. A [56] References Cited compression spring provided with spacers is arranged within a tubular casing having interior walls coated with a low-friction UNITED TATE PATEN material to facilitate aligned compression of the spring. 1,703,397 2 1929 Kirk ..267/8 calibaFed mad mm are "ranged 2 159 S70 5/1939 we" 248/54 R rately display the load Imposed thereon.

1 Wood a 6 r i g Figures PAIENIED JANZSIHTZ 375337; 174

Ilium?!" INVENTOR UH! SHE VG KUO ATTORNEYS mmu M3125 m2 WW Mi" INVENTOR CHI SHEA/G KUO SPRING HANGER FIELD OF THE INVENTION The present invention relates generally to spring hangers for suspending tubular structures. More particularly, the invention relates to a spring hanger adapted to suspend tubular furnace coils. The invention is especially applicable for use in suspending vertically .disposed serpentine coils in high temperature, high severity, hydrocarbon cracking furnaces.

BACKGROUND OF THE INVENTION Description of the Prior Art Furnaces used to heat fluids are provided with furnace tubes or tubular coils through which the fluid flows. The furnace tubes are suspended in the furnace firebox by various means, such .as counterweighted hangers, tension spring hangers or compression spring hangers.

Furnace tubes have exceedingly low mechanical strengths at high crackling temperatures and the supporting force exerted by the hangers greatly affects the stress level of the supported tubes. Therefore, regardless of the type of hanger used, care must be taken in the design thereof to avoid the possibility of imposing an unsafe stress on the furnace tubes. To accomplish this, a hanger must be able to accurately show the magnitude of the force exerted by the tubes and to permit accurate adjustment of the force exerted by the individual hangers.

At present, furnace tube hangers are generally mounted on a structure outside the furnace to avoid exposure to the heat within the furnace and to facilitate inspection and maintenance thereof. Therefore, the furnace tube hangers areexposed to changing ambient temperatures and corrosive atmospheres which tend to vary the hanger characteristics. Accordingly, the initial design of the furnace tube hangers must also comprehend the likely effects of these factors.

Basically, furnace tube hangers must be designed to maintain precision in service and reliabilitysTherefore, it is desirable to design a furnace tube hanger which is simple in operation and reliable.

The counterweight design adapted to suspend furnace tubes, as seen in US. Pat. No. 3,385,269 (Breckenridge; issued May 28, 1968) is simple in construction, but requires a considerable amount of space for operation. This in turn increases the cost of support structures. Moreover, the counterweight design lacks the expansion characteristics of a spring hanger and has a tendency to impose stress on the tubes.

Tension spring hangers are generally of simple construction. Basically, they are comprised essentially of tension or extension springs designed to resist elongation as a force is exerted on each end. However, they necessarily require alarge vertical distance to operate when designed to provide the same support that compression springs provide. As a result,.tension spring hangers need a larger operating area and a taller support structure.

To the contrary, compression springs can be made compact and used in a smaller area. This benefit is afforded mainly because compression springs do not have lengthy end loops and can be shortened by precompression. It should be noted that extension springs can also be shortened by pretension, but not as effectively as compression springs.

Basically, there are two types of conventional hangers using compression springs, the variable spring support hangerand the constant support hanger.

The variable spring support hanger is comprised essentially of a compression spring and a hanger casing. The variable spring support lacks means to prevent the compression spring from deflecting laterally against the hanger casing. Consequently, a substantial amount of sliding friction force is generated between the spring and the casing, which force will impose dangerous stress on the furnace tubes. Additionally, this type of compression spring hanger does not have a sufficientlyflexible joint between the suspension rod and the compression spring. Whenever the suspension rod is subjected to a small lateral movement from the supported tubes, the spring will tilt and consequently induce more sliding friction and change the spring performance characteristics. Moreover, this type of hanger has a long and'wide longitudinal opening along thecasing for the purpose of load indication. Foreign bodies. such as sand, grit and stray metal particles can easily fall through the slot opening into the casing interior. The presence of foreign material will induce additional friction between the casing wall and the compression spring and in extreme cases jam the spring. I

The constant support hanger is usually arranged perpendicularly to the force which it reacts. Consequently, the constant support hanger requires a precision engineered, complex mechanical linkage to transmit the vertical force imposed by r the tubes to the compression spring. In general, this type of hanger can exert an accurate supporting force when new; however, it quickly becomes less accurate since the supporting force changes greatly with very slight bearing wear or surface deformation in the linkage joints. Additionally, the complexity of the mechanism makes it very difficult to obtain any fine adjustment of the hanger force on a job site. Moreover, the constant support hanger is very expensive.

Therefore, none of the presently known spring hangers utilize a compression spring which can be arranged in a simple, accurate, reliable and inexpensive assembly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inexpensive spring hanger employing a compression spring which is maintained in vertical alignment.

It is a further object of the present invention to provide. an accurate spring hanger which includes provision for adjusting the hanger because of thedifference in the weight of the tubes and the elastic effects of the piping and which further includes means for accurately indicating the relative load on the spring.

To this end, a spring hanger is provided which is comprised essentially of a tubular casing member, a compression spring adapted to fit within the casing member and a hanger suspen' sion rod assembly to attach the hanger to a furnace tube. The tubular casing is cylindrically shaped, has a top and bottom closure member and is formed with an inside diameter slightly larger than the outer periphery of the compression spring. Also, the interior wall of the casing is coated with a low-friction material to reduce the friction force between the wall and the compression spring. The compression spring rests on the casing bottom closure member andoccupies essentially the entire height of the casing during the unloaded condition. The hanger suspension rod assembly includes an upper disc member which seats on the top of the compression spring and the hanger suspension rod which depends from the piston cap member axially within the hanger assembly. The hanger suspension rod terminates in a connection member for direct attachment to a furnace tube. Centering rings located on the lower surface of the disc and the upper surface of the bottom casing closure member serve to confine the spring in vertical alignment. In addition, an intermediate spring spacer is provided to further insure alignment of the spring. Both the upper disc member and the intermediate spring spacer have a peripheral array of low-friction resilient bumpers which prevent contact between the casing interior and the spring.

A calibration scale is also provided to indicate the force imposed on the hanger by the tube. The calibration scale is preferably mounted onthe hanger suspension rod and can be adjusted to indicate a basic load (design load) with respect to any convenient reference point. With the suspension rod adapted to travel vertically along the axis of the spring hanger, any variation in load will appear as the rod is depressed.

DESCRIPTION OF THE DRAWINGS The invention will be described hereinafter with reference to the following-drawings wherein:

FIG. I is an elevational view, partially in section, of a furnace having vertically disposed tubes suspended by the spring hangers of the present invention;

FIG. 2 is an elevational view in section of the spring hangers of the present invention;

FIG. 3 is a cross-sectional view of the spring hanger of FIG. 2 taken through line 3-3;

FIG. 4 is a cross-sectional view of the spring hanger of FIG. 2 taken through line 44;

FIG. 5 is a cross-sectional view of the spring hanger of FIG. 2 taken through line 55; and

FIG. 6 is an elevational view of an alternative embodiment of the spring hanger of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The spring hanger of the present invention can be used to suspend pipelines in virtually any application. However, the spring hanger is particularly suitable for suspending vertically disposed tubes in high severity cracking furnaces. Therefore, for illustrative purposes, the spring hangers of the present invention are shown suspending a vertically disposed serpentine coil in a cracking furnace designed primarily to thermally crack hydrocarbon feed to produce olefins.

A typical high severity cracking furnace 2, shown in FIG. 1, is provided with a cracking section 4 and a convection section 6 which is offset from the cracking section 4. The cracking tubes 8 which are vertically disposed and form a serpentine coil 10 are located in the cracking section 4. The cracking tubes 8 are suspended by spring hangers 12 designed in accordance with the present invention.

A steel structural beam 14 is arranged above the roof 16 of the cracking section 4 on supports 18 to accommodate the spring hangers 12. The beam 14 and the spring hangers 12 depending downwardly therefrom are in the same vertical plane with the upper U-bends 20 of the coil 10. The roof 16 of the cracking section 4 is provided with a plurality of holes 22 to afford access to the coil U-bends 20.

As best seen in FIG. 2, the spring hanger 12 is comprised of a casing member 24, a compression spring 26 and a suspension rod assembly 28 mounted on the compression spring 26.

The casing member 24 is essentially cylindrical and is provided with a top cap 30 and a bottom cap 32. The top cap 30 is completely closed and serves the dual functions of protecting the interior of the casing member 24 from dust and any foreign particles which might be inimical to the operation of the hanger, and to accommodate means for attaching the spring hanger 12 to a fixed structure. Illustrative of the various means for attaching the spring hanger is a top cap 30 which is welded to the casing 24 and sized to extend beyond the outer edge of the casing 24 to form a flange 34 having a plurality of holes 36 for attachment bolts 38. The bolts 38 pass through the holes 36 and aligned holes 40 in the structural beam 14 to rigidly mount the spring hanger 12. Thus, the spring hanger 12 will be restrained from any vibration or other movement normally caused by the wind. The bottom cap 32 is provided with an axial opening 42 to allow the suspension rod assembly 28 to pass unimpededly. The casing interior is coated or lined with a low-friction surface 44 which is provided to reduce the friction forces generated as the compression spring 26 contracts and expands. TEFLON (tetrafluoroethylene), nylon and epoxy resin have all proved to be satisfactory materials to form the surface 44.

The compression spring 26 is arranged within the casing 24 and adapted to rest on the bottom cap 32. While a variety of springs can be used, practice has taught that a compression spring made of Cr-Si alloy steel (ASTM A401 or SAE 9262) is particularly suitable. Essentially, the outer periphery of the compression spring 26 is slightly smaller than the diameter of the interior low-friction surface 44 of the casing 24. The presence of only a small allowance between the casing surface 44 and the outer periphery of the compression spring 26 obviates any consequential tendency in the compression spring 26 to buckle since the casing acts to confine the spring in a vertically aligned orientation.

The suspension rod assembly 28 is comprised primarily of a suspension rod 46, a disc 48 and means (not shown) to attach the suspensionrod 46 to a tube or pipe U-bend. The suspension rod 46 terminates in a ring 50 and the disc 48 is provided with a U-shaped attachment member 70 depending from the 7 center of the disc lower surface. The ring 50 attaches to the U- shaped attachment member 70 to connect the suspension rod 46 to the disc 48. The U-shaped member 70 and ring 50 afford plural articulation for the suspension rod 46, thereby minimizing tilting of the disc 48 which might result if the furnace tubes are deflected. The combination of rigidly mounting the casing 24 and providing an articulated suspension rod assembly 28 affords the spring hanger 12 with protection from outside forces, such as wind forces, and means to compensate for the tube deflections. If universal mounting of the suspension rod 46 is found necessary, a universal joint can be used as the connecting means. In addition, a turnbuckle 54 is arranged as part of the suspension rod 46. The disc 48 is configured similarly to the interior cross section of the casing 24 as shown in FIG. 3 and is adapted to rest on the upper surface of the compression spring 26. The disc 48 is provided with a peripheral array of resilient low-friction bumpers 52 which can be formed of TEFLON or nylon. These bumpers 52 provide a low-friction sliding member to cooperate with the coating surface 44 on the interior of the casing 24. The bumpers 52 serve to center the upper end of the compression spring 26 to thereby prevent the spring 26 from buckling and to prevent sharp edges of the upper end of the compression spring 26 from cutting into the coating surface 44.

In addition, the spring hanger 12 is provided with means to prevent or to minimize the amount of the contact between the outer surface of the compression spring 26 and the inner wall 44 of the casing 24. Any friction force imposed by the wall on the compression spring 26 is inimical to the furnace tube life since the force is ultimately transmitted to the furnace tube. As shown in FIG. 2 for illustrative purposes, the compression spring 26 is split into two longitudinal sections 26a and 26b with an intermediate spring spacer 56 inserted between the adjacent sections 26a and 26b. It should be noted that more than two spring sections can be used in the spring hanger of the present invention. However, it is necessary to use a spring spacer 56 between each spring section regardless of the number of spring sections used.

The spring spacer 56 shown in FIGS. 2 and 4, has a sleevelike configuration, with the outer surface being dimensioned to the size of the inner periphery of the compression spring 26. Also, an outer annular peripheral rib 58 is located intermediately on the outer surface of the spring spacer 56. The outer annular peripheral rib 58 is sized to extend from the outer surface of the spring spacer 56 beyond the outer periphery of the compression spring 26 into proximity with the interior surface 44 of the casing 24. A peripheral array of resilient low-friction bumpers 60, seen in FIG. 4, is mounted on the rib 58. The bumper members 60 can be formed of any low-friction material such as nylon or TEFLON. Functionally, the spring spacer 56 serves to support the compression spring 26 from radial deflection. The bumpers 60 combine with the bumpers 52 on the disc 48 to provide a sliding surface which can engage the low-friction casing interior surface 44. As a consequence, the likelihood of the compression spring 26 engaging the casing interior surface 44 is greatly minimized.

Additional means to maintain the compression spring 26 in vertical alignment are provided in the form of upper and lower centering rings 62 and 64. The centering rings 62 and 64 are configured similarly to the interior of the compression spring 26 and function to fixedly locate the compression spring 26. Both the upper and lower centering rings are arranged concentrically with the casing 24 and are in alignment with each other. The lower centering ring, best seen in FIG. 5, is fixedly secured to the inner surface of the bottom casing cap 32 and extends upwardly. The upper centering ring 62 is fixed to the lower surface of the disc 48 and depends downwardly. The combination of the upper centering ring 62, the lower centering ring 64, the intermediately arranged. spring spacer 56 and the casing 24 confines the compression spring 26 in a substantially vertically aligned orientation.

A calibrated load indicator 66, shown in FIGS. 2, 4 and 5, is arranged on the spring hanger 12. This load indicator 66 is graduated and numbered according to the relative distance of the spring compression, such as shown in FIG. 2, or according to the magnitude of the load exerted.

The calibrated load indicator 66 is designed to be movably mounted on the suspension rod 46, and when fixedly attached to the suspension rod 46, is adapted to translate with the suspension rod with respect to a fixed reference position on the spring hanger 12. In practice, it has been found that this reference position can be the bottom face of the bottom cap 32. Also, it has been found than an appropriately calibrated sleeve sized to fit around the suspension rod 46 is a particularly suitable load indicator. A setscrew 68 is provided to temporarily lock the sleeve in place at any point on the suspension rod. The setscrew 68 will be removed after the hanger 12 has been calibrated. a

The hanger 12 is calibrated before it is put into service. Calibration of the hanger is essentially to secure a permanent reference position of the load indicator 66 together with the suspension rod 46 relative to a fixed reference position while the hanger is pulled down by a given basic load. The choice of the bottom of the casing as the fixed reference position has already been discussed. The basic load can be a convenient value close to or equal to the anticipated average hanger load in service.

The calibration for the hanger 12 can be accomplished by the following sequential steps. Apply a load equal to the basic load to the hanger at the suspension rod 46. Position the load indicator 66 by resetting the setscrew 68 so that the graduation corresponding to the basic load on the load indicator 66 is aligned with the fixed reference position of the hanger 12. Remove the load from the hanger. Permanently tack weld the load indicator 66 to the suspension rod 46. The hanger 12 is now ready for service.

In operation, the hanger 12 is mounted on the support beam 14 by bolts 38. Next, the suspension rod 46 is connected to the upper Ubend of the tube being supported. The turnbuckle 54 can then be adjusted to insure that a satisfactory relationship between the tube and tube hanger 12 is present. In practice, it has been found that the required load for the hanger generally differs from the basic load on which the calibration of the hanger has been based. One of the reasons is due to the weight tolerance of the tube. To obtain the required load for the hanger 12, the turnbuckle 54 is adjusted until the graduation corresponding to the new load is aligned with the bottom of the casing.

FIG. 6 shows an alternative embodiment of the spring hanger of the invention. Compared with the hanger shown in FIG. 2, this alternative greatly shortens the overall length of the hanger and thereby reduces the required height of the support structure.

The present hanger embodiment shown in FIG. 6 includes two concentrically arranged casing members 124 and 127 with compression springs 126 and 129 arranged respectively therein. The outer casing 124 is provided with a top cap 130 which extends beyond the outer edge of the casing 124 to form a flange 134 provided with a plurality of holes 136 to facilitate attachment to a structural beam. The casing 124 also includes a bottom inwardly directed flange 125 adapted to support the compression spring 126. The flange 125 also includes a plurality of bumpers 152 essentially identical to the TEFLON or nylon bumpers 52 shown in the embodiment of FIG. 2. A lower centering ring 164 is provided on the inwardly directed flange 125 maid in maintaining the spring 126 in vertical alignment.

The inner casing 127 is provided with a bottom cap 132 and an upper outwardly directed flange 133. The bottom of the flange 133 rests on the spring 126 arranged in the outer casing 124 and the bottom cap 132 forms the support surface for the spring 129. A centering ring 162 depends from the bottom of the flange 133 to provide proper centering for the spring 126. A suspension rod assembly 128 is comprised of a suspension rod 146 terminating in a ring 150, a disc 148, a U-shaped member 170 arranged to cooperate with the ring 151) to connect disc 148 and the rod 146 and a turnbuckle 154. The disc 148 is arranged to bear against the top of spring 129 and react the force from the furnace tube or pipe to the spring hanger. Inner centering rings 172 and 174 depending from the disc 148 and extending upwardly from the bottom cap 132 respectively, serve to maintain the spring 129' in vertical alignment. Peripherally arranged bumpers 160 and 176 extend from the inner flange 133 and the disc 143 respectively, to providc means to prevent the springs 126 and 129 from contacting the casing inner walls.

The inner wall of the outer casing ll24 is provided with a surface 144 of low-friction material, such as TEFLON, nylon or an epoxy resin, similar to the surface 44 of the embodiment shown in FIG. 2. The inner and outer surfaces of the inner casing 127 are provided with coatings 145 and 147 respectively, which are essentially the same as thecoating 44 shown in the embodiment of FIG. 2.

The calibration means depicted is functionally identical, but a structural variation of the calibration. means shown in FIG. 2. Basically, the calibration means includes a load indicator 166 and a temporary fastening screw 168 and is adapted to be calibrated in the same fashion as previously described.

While the preferred embodiments have been described as having low-friction coatings on the casing walls, it should be noted that low friction coatings on the spring members can also be employed.

The hanger of the present invention can maintain a high degree of accuracy in both force indication and force adjustment while it permits the use of liberal manufacturing tolerances for the compression spring and the other components. For example, a 10 percent tolerance in the spring constant will not induce a force deviation of more than I percent, if the difference between the required load and the calibrating basic load is within 10 percent. Also, it should be noted that the overall force inaccuracy of the hanger invention can be readily kept to within 2 percent while that of the conventional variable spring support is usually as high as l5 percent.

Iclaim:

1. A spring hanger for suspending pipelines comprising:

an upper and lower compression spring arranged in vertical axial alignment;

a casing having an opening in the bottom thereof to house the compression spring means;

a spring spacer located between the upper and lower compression springs to maintain the compression spring means in veftical axial alignment, which spring spacer has an outer surface sized to conform to the inner diameter of the compression springs, a peripheral rib formed on the outer surface of the spring spacer, which rib is adapted to extend beyond the outer surface of the outer periphery of the compression springs;

a plurality of bumpers formed of low-friction material which bumpers are peripherally disposed on the rib; and

a suspension assembly adapted to suspend the pipeline from the spring hanger and transmit the load from the pipeline to both compression springs simultaneously.

2. An apparatus as in claim 1 wherein the suspension asi sembly is comprised of a disc adapted to bear against the top of the upper compression spring member, which disc is smaller in diameter than the inner diameter of the casing and a suspension rod connected at one end to the disc and at the other end to the pipe being suspended.

3. An apparatus as in claim 2 wherein the suspension assembly further comprises a plurally articulated joint adapted to connect the piston suspension rod to the disc and a turnbuckle in the suspension rod.

4. An apparatus as in claim 3 further comprising a plurality of bumpers formed of low-friction material which bumpers are peripherally disposed on the disc bearing against the top of the upper compression spring.

5. An apparatus as in claim 4 further comprising means to indicate the load imposed on the compression spring.

6. A spring hanger for suspending pipelines comprising:

compression spring means;

means to house the compression spring means;

means to maintain the compression spring means in vertical axial alignment;

a suspension rod assembly adapted to suspend the pipeline from the spring hanger;

a calibrated sleeve slidably mounted on the suspension rod to indicate the load on the compression spring; and

means to rigidly fix the sleeve on the suspension rod at any point thereon.

7. An apparatus as in claim 6 further comprising means to locate the compression spring in the casing.

8. An apparatus as in claim 7 wherein the means to house the compression spring means in a cylindrical casing having a casing bottom and the suspension rod assembly includes a disc which bears on the top of the compression spring and the means to locate the compression spring in the casing is comprised of a first centering ring extending upwardly from the inner surface of the casing bottom and a second centering ring depending from the lower surface of the disc of the suspension rod assembly.

9. A spring hanger for suspending pipelines comprising:

an outer compression spring;

an inner compression spring arranged concentrically within the outer compression spring;

an outer casing;

a flange extending inwardly from the outer casing adapted to support the outer compression spring;

an inner casing;

a flange extending outwardly from the top of the inner casing adapted to bear on the top of the outer compression spring;

an inner casing bottom having a centrally disposed hole therein, said casing bottom adapted to support the inner compression spring;

a plurality of bumpers formed of low-friction material arranged on the outer peripheral surface of the flange extending outwardly from the inner casing;

a plurality of bumpers formed of low-friction material arranged on the inner peripheral surface of the flange extending inwardly from the outer casing;

a plurality of bumpers formed of low-friction material arranged on the periphery of the disc bearing on the inner compression spring; and

a suspension rod assembly adapted to suspend the pipeline from the spring hanger.

10. An apparatus as in claim 9 further comprising low-friction coatings on the inner surface of the outer housing and the inner surface of the inner housing.

11. An apparatus as in claim 10 further comprising a lowfriction coating on the outer wall of the inner casing.

12. An apparatus as in claim 10 wherein the suspension assembly is comprised of a disc adapted to bear against the top of the inner compression spring, which disc is smaller in diameter than the inner diameter of the inner casing and a suspension rod connected at one end to the disc and at the other to the pipe being suspended.

13. An apparatus as in claim 12 wherein the suspension assembly further comprises a plurally articulated joint adapted to connect the suspension rod to the disc and a turnbuckle in the suspension rod.

14. An apparatus as in claim 9 further comprising means to indicate the load imposed on the compression spring.

15. An apparatus as in claim 14 wherein the means to indicate the load in the compression spring is comprised of a calibrated indicator slidably mounted on the suspension rod and means to rigidly fix the indicator to the suspension rod at ani goint thereon.

. An apparatus as in claim 15 further comprising means to locate the inner compression spring and the outer compression spring.

17. An apparatus as in claim 16 wherein the means to locate the inner compression spring is a centering ring extending upwardly from the bottom cap of the inner casing and a centering ring depending from the lower surface of the disc bearing on the inner compression spring and the means to locate the outer compression spring is a centering ring extending upwardly from the flange extending inwardly from the outer casing and a centering ring depending from the flange extending outwardly from the inner casing. 

1. A spring hanger for suspending pipelines comprising: pipe lines an upper and lower compression spring arranged in vertical axial alignment; a casing having an opening in the bottom thereof to house the compression spring means; a spring spacer located between the upper and lower compression springs to maintain the compression spring means in vertical axial alignment, which spring spacer has an outer surface sized to conform to the inner diameter of the compression springs, a peripheral rib formed on the outer surface of the spring spacer, which rib is adapted to extend beyond the outer surface of the outer periphery of the compression springs; a plurality of bumpers formed of low-friction material which bumpers are peripherally disposed on the rib; and a suspension assembly adapted to suspend the pipe line from the spring hanger and transmit the load from the pipe line to both compression springs simultaneously.
 2. An apparatus as in claim 1 wherein the suspension assembly is comprised of a disc adapted to bear against the top of the upper compression spring member, which disc is smaller in diameter than the inner diameter of the casing and a suspension rod connected at one end to the disc and at the other end to the pipe being suspended.
 3. An apparatus as in claim 2 wherein the suspension assembly further comprises a plurally articulated joint adapted to connect the piston suspension rod to the disc and a turnbuckle in the suspension rod.
 4. An apparatus as in claim 3 further comprising a plurality of bumpers formed of low-friction material which bumpers are peripherally disposed on the disc bearing against the top of the upper compression spring.
 5. An apparatus as in claim 4 further comprising means to indicate the load imposed on the compression spring.
 6. A spring hanger for suspending pipelines comprising: compression spring means; means to house the compression spring means; means to maintain the compression spring means in vertical axial alignment; a suspension rod assembly adapted to suspend the pipeline from the spring hanger; a calibrated sleeve slidably mounted on the suspension rod to indicate the load on the compression spring; and means to rigidly fix the sleeve on the suspension rod at any point thereon.
 7. An apparatus as in claim 6 further comprising means to locate the compression spring in the casing.
 8. An apparatus as in claim 7 wherein the means to house the compression spring means in a cylindrical casing having a casing bottom and the suspension rod assembly includes a disc which bears on the top of the compression spring and the means to locate the compression spring in the casing is comprised of a first centering ring extending upwardly from the inner surface of the casing bottom and a second centering ring depending from the lower surface of the disc of the suspension rod assembly.
 9. A spring hanger for suspending pipelines comprising: an outer compression spring; an inner compression spring arranged concentrically within the outer compression spring; an outer casing; a flange extending inwardly from the outer casing adapted to support the outer compression spring; an inner casing; a flange extending outwardly from the top of the inner casing adapted to bear on the top of the outer compression spring; an inner casing bottom having a centrally disposed hole therein, said casing bottom adapted to support the inner compression spring; a plurality of bumpers formed of low-friction material arranged on the outer peripheral surface of the flange extending outwardly from the inner casing; a plurality of bumpers formed of low-friction matErial arranged on the inner peripheral surface of the flange extending inwardly from the outer casing; a plurality of bumpers formed of low-friction material arranged on the periphery of the disc bearing on the inner compression spring; and a suspension rod assembly adapted to suspend the pipeline from the spring hanger.
 10. An apparatus as in claim 9 further comprising low-friction coatings on the inner surface of the outer housing and the inner surface of the inner housing.
 11. An apparatus as in claim 10 further comprising a low-friction coating on the outer wall of the inner casing.
 12. An apparatus as in claim 10 wherein the suspension assembly is comprised of a disc adapted to bear against the top of the inner compression spring, which disc is smaller in diameter than the inner diameter of the inner casing and a suspension rod connected at one end to the disc and at the other to the pipe being suspended.
 13. An apparatus as in claim 12 wherein the suspension assembly further comprises a plurally articulated joint adapted to connect the suspension rod to the disc and a turnbuckle in the suspension rod.
 14. An apparatus as in claim 9 further comprising means to indicate the load imposed on the compression spring.
 15. An apparatus as in claim 14 wherein the means to indicate the load in the compression spring is comprised of a calibrated indicator slidably mounted on the suspension rod and means to rigidly fix the indicator to the suspension rod at any point thereon.
 16. An apparatus as in claim 15 further comprising means to locate the inner compression spring and the outer compression spring.
 17. An apparatus as in claim 16 wherein the means to locate the inner compression spring is a centering ring extending upwardly from the bottom cap of the inner casing and a centering ring depending from the lower surface of the disc bearing on the inner compression spring and the means to locate the outer compression spring is a centering ring extending upwardly from the flange extending inwardly from the outer casing and a centering ring depending from the flange extending outwardly from the inner casing. 